I updated an older Ubuntu 18.04 LTS system to the latest LTS and had (among other things) Docker and KVM installed. KVM is actually quite nice if you "just need" a small VM (pfsense ;)). I actually prefer Proxmox and ESXi, but hey, the right tool for the right job.
After the upgrade to 20.04, kvm did not work anymore and I got a lot of lvm2 errors during apt update / apt upgrade sessions, so a short google later I found this. I was a bit nervous, but the fix did neither hurt my kvm nor my Docker instances
sudo apt purge lvm2 && sudo apt install lvm2
(The fix is deleting and reinstalling lvm2)
After reinstalling lvm2, I could successfully execute a virsh list and got my list of running KVM machines back:
Id Name State ------------------------- 1 pfsense running